Prazi Pro from Hikari might be worth trying.

http://www.uskoi.com/prazipro.htm

Its a general fluke and flatworm treatment. It may be chemically similar to Flatworm Exit but a lot less expensive. It would be worth a try to see if it works as a dip treatment product or as a general tank treatment. I'm not sure who carries it locally, but I do know that CB pets does. If someone does try it, please report back.